1This is what POSIX 2003 says about ps: 2 3By default, ps shall select all processes with the same effective user 4ID as the current user and the same controlling terminal as the invoker 5 6ps [-aA][-defl][-G grouplist][-o format]...[-p proclist][-t termlist] 7[-U userlist][-g grouplist][-n namelist][-u userlist] 8 9-a Write information for all processes associated with terminals. 10 Implementations may omit session leaders from this list. 11 12-A Write information for all processes. 13 14-d Write information for all processes, except session leaders. 15 16-e Write information for all processes. (Equivalent to -A.) 17 18-f Generate a full listing. (See the STDOUT section for the con- 19 tents of a full listing.) 20 21-g grouplist 22 Write information for processes whose session leaders are given 23 in grouplist. The application shall ensure that the grouplist is 24 a single argument in the form of a <blank> or comma-separated 25 list. 26 27-G grouplist 28 Write information for processes whose real group ID numbers are 29 given in grouplist. The application shall ensure that the grou- 30 plist is a single argument in the form of a <blank> or comma- 31 separated list. 32 33-l Generate a long listing. (See STDOUT for the contents of a long 34 listing.) 35 36-n namelist 37 Specify the name of an alternative system namelist file in place 38 of the default. The name of the default file and the format of a 39 namelist file are unspecified. 40 41-o format 42 Write information according to the format specification given in 43 format. Multiple -o options can be specified; the format speci- 44 fication shall be interpreted as the <space>-separated concate- 45 nation of all the format option-arguments. 46 47-p proclist 48 Write information for processes whose process ID numbers are 49 given in proclist. The application shall ensure that the pro- 50 clist is a single argument in the form of a <blank> or comma- 51 separated list. 52 53-t termlist 54 Write information for processes associated with terminals given 55 in termlist. The application shall ensure that the termlist is a 56 single argument in the form of a <blank> or comma-separated 57 list. Terminal identifiers shall be given in an implementation- 58 defined format. On XSI-conformant systems, they shall be 59 given in one of two forms: the device's filename (for example, 60 tty04) or, if the device's filename starts with tty, just the 61 identifier following the characters tty (for example, "04" ). 62 63-u userlist 64 Write information for processes whose user ID numbers or login 65 names are given in userlist. The application shall ensure that 66 the userlist is a single argument in the form of a <blank> or 67 comma-separated list. In the listing, the numerical user ID 68 shall be written unless the -f option is used, in which case the 69 login name shall be written. 70 71-U userlist 72 Write information for processes whose real user ID numbers or 73 login names are given in userlist. The application shall ensure 74 that the userlist is a single argument in the form of a <blank> 75 or comma-separated list. 76 77With the exception of -o format, all of the options shown are used to 78select processes. If any are specified, the default list shall be 79ignored and ps shall select the processes represented by the inclusive 80OR of all the selection-criteria options. 81 82The -o option allows the output format to be specified under user con- 83trol. 84 85The application shall ensure that the format specification is a list of 86names presented as a single argument, <blank> or comma-separated. Each 87variable has a default header. The default header can be overridden by 88appending an equals sign and the new text of the header. The rest of 89the characters in the argument shall be used as the header text. The 90fields specified shall be written in the order specified on the command 91line, and should be arranged in columns in the output. The field widths 92shall be selected by the system to be at least as wide as the header 93text (default or overridden value). If the header text is null, such as 94-o user=, the field width shall be at least as wide as the default 95header text. If all header text fields are null, no header line shall 96be written. 97 98ruser The real user ID of the process. This shall be the textual user 99 ID, if it can be obtained and the field width permits, or a dec- 100 imal representation otherwise. 101 102user The effective user ID of the process. This shall be the textual 103 user ID, if it can be obtained and the field width permits, or a 104 decimal representation otherwise. 105 106rgroup The real group ID of the process. This shall be the textual 107 group ID, if it can be obtained and the field width permits, or 108 a decimal representation otherwise. 109 110group The effective group ID of the process. This shall be the textual 111 group ID, if it can be obtained and the field width permits, or 112 a decimal representation otherwise. 113 114pid The decimal value of the process ID. 115 116ppid The decimal value of the parent process ID. 117 118pgid The decimal value of the process group ID. 119 120pcpu The ratio of CPU time used recently to CPU time available in the 121 same period, expressed as a percentage. The meaning of 122 "recently" in this context is unspecified. The CPU time avail- 123 able is determined in an unspecified manner. 124 125vsz The size of the process in (virtual) memory in 1024 byte units 126 as a decimal integer. 127 128nice The decimal value of the nice value of the process; see nice() . 129 130etime In the POSIX locale, the elapsed time since the process was 131 started, in the form: [[dd-]hh:]mm:ss 132 133time In the POSIX locale, the cumulative CPU time of the process in 134 the form: [dd-]hh:mm:ss 135 136tty The name of the controlling terminal of the process (if any) in 137 the same format used by the who utility. 138 139comm The name of the command being executed ( argv[0] value) as a 140 string. 141 142args The command with all its arguments as a string. The implementa- 143 tion may truncate this value to the field width; it is implemen- 144 tation-defined whether any further truncation occurs. It is 145 unspecified whether the string represented is a version of the 146 argument list as it was passed to the command when it started, 147 or is a version of the arguments as they may have been modified 148 by the application. Applications cannot depend on being able to 149 modify their argument list and having that modification be 150 reflected in the output of ps. 151 152Any field need not be meaningful in all implementations. In such a case 153a hyphen ( '-' ) should be output in place of the field value. 154 155Only comm and args shall be allowed to contain <blank>s; all others 156shall not. 157 158The following table specifies the default header to be used in the 159POSIX locale corresponding to each format specifier. 160 161 Format Specifier Default Header Format Specifier Default Header 162 args COMMAND ppid PPID 163 comm COMMAND rgroup RGROUP 164 etime ELAPSED ruser RUSER 165 group GROUP time TIME 166 nice NI tty TT 167 pcpu %CPU user USER 168 pgid PGID vsz VSZ 169 pid PID 170 171There is no special quoting mechanism for header text. The header text 172is the rest of the argument. If multiple header changes are needed, 173multiple -o options can be used, such as: 174 175 ps -o "user=User Name" -o pid=Process\ ID 176